Facial contour and geometry are being used to design masks and to identify mask usage in many medical fields including CPAP (constant positive air pressure). CPAP masks are used to provide a breathable mixture of gases, typically air, provided at above ambient pressure to a patient. A CPAP mask forms a seal around a nose and mouth of a patient's face, providing an interface between the air source and the patient's respiratory system that is ideally free of leaks. CPAP masks are used in a wide variety of medical treatment procedures.
A CPAP mask comprises a dome and a cuff, which forms a seal around the patient's face. The dome fits over the patient's nose and mouth, and provides a conduit to the source of air. Ideally, the seal is air-tight under the pressure in normal service. Typically, cuffs in CPAP masks comprise silicone gaskets, and other materials with similar properties of high elasticity. The problem which the cuffs in CPAP masks often lead to is irritation around the face of the patient. This is particularly found in medical environments, where the masks may be worn for hours or days without changing or removing from the face. This occurs because silicone gaskets often do not seal well to the patient's face, especially around the bridge and lower sides of the nose. The resulting air leaks into the patient's eyes, causing eye irritation. These air leaks can be avoided by pushing the CPAP mask more tightly to the patient's face. However this pressure can lead to minor red marks or open sores. Additionally, individuals have widely varying sensitivities to mechanical pressure. A combination of skin and eye irritation reduces patient tolerance and compliance with the medical procedure utilizing the mask.
CPAP masks often will not acceptably seal to a face with wrinkles or other irregularities, as it is often found in older persons that commonly employ CPAP procedures. In order to maximize compliance for the CPAP therapy, the CPAP masks have to be customized and to be adjusted as well as possible to the patient's face. Therefore the facial contour and geometry of the patient's face has to be captured for customizing the CPAP masks. There have been many attempts to capture such data digitally with non-contact methods, such like digital scans. However, the known methods run into the issue of facial hairs, deep lines and wrinkles, which create noises to the 3D digital models. These noises prevent to accurately identify the landmarks of the object to be measured.